1. Field of the Invention
The present invention relates to a cutting machine tool such as for wood working and iron working and, in particular, to a working table apparatus for the cutting machine tool for positioning and securing a work or works thereon.
2. Description of Background Art
In general, with cutting machine tools such as a milling machine or router for wood working, the mounting and removal of a work on the working table of the machine tool has been carried out using clamping members and bolts adapted to be fastened and loosened by a spanner in a well-known manner. More recently, it has been proposed to clamp the wood on a jig secured on the working table using fluidic or electromagnetic force.
Although the conventional clamping apparatus using the clamping members and bolts is easy to manufacture, it is inferior in clamping efficiency and thus its use is limited to single or small-quantity production applications. On the other hand, the automatic or semi-automatic clamping arrangement using the jig, while superior in clamping efficiency, is costly to manufacture and requires substantial time for mounting the jig.
In order to overcome the problems mentioned above, in recent years there has been developed a clamping method in which the work is clamped on a top plate covering the top surface of the working table by negative pressure supplied through suction ports formed in the top plate from a negative pressure chamber formed in the under surface of the top plate (see, for example, Japanese Utility Model Registration Gazette No. 2503256).
However, in high volume production applications, positioning efficiency suffers if the machining specification and the sliding direction of the working table have to be set each time the works are fed onto the working table. Accordingly, it is known to eliminate the positioning adjustment by initially adjusting the position of one or more locating pins or locating blocks on the working table and then positioning the work or works by abutting the reference surface of the work against the locating pins or blocks.
Although the method using locating pins or blocks makes the mounting and removal operation remarkably easy, it also suffers the serious disadvantage that the locating pins or blocks often interfere with tools mounted on the spindles of the machine tool causing damage to either the locating pins or blocks or to the tools.
In addition, the locating pins or blocks must be exchanged whenever works of different sizes are to be machined.
Furthermore, operation of the machine tool must be stopped for a long period of time to mount, adjust, and/or remove a large number of pins or blocks when the works to be machined are small in size or great in number.
In addition, when works are positioned by abutting them against the locating pins or blocks, a positioning error frequently occurs as a result of imperfect contact between the work and the locating pins or blocks.
Moreover, when using negative pressure or electromagnetic force to clamp works onto the working table, the required operating buttons or actuating elements are usually mounted on the bed of the machine tool. Consequently, the distance between the working table and the actuating elements is increased whenever the working table is moved to its extreme positions thus making the clamping operation difficult.